Double Glazing Noise Reduction in dB: What the Numbers Actually Mean
Understanding double glazing noise reduction in dB helps you make sense of the performance claims you will encounter when comparing window products. Decibels are the standard unit for measuring sound levels and sound reduction, but they work on a logarithmic scale that is not intuitive, and the numbers printed on product specifications do not always tell the full story about real-world performance. This guide explains what the dB figures mean, what drives them, and what you can realistically expect from a quality double glazed window installation.
How Decibels Work and Why It Matters
The decibel scale is logarithmic, which means the relationship between numbers is not linear. A sound that is 10 decibels louder than another is not simply a little louder, it is perceived as roughly twice as loud. A 20 decibel difference is perceived as about four times as loud. A 30 decibel difference is roughly eight times as loud.
This means that double glazing noise reduction in dB figures that might look modest are actually significant in practice. A window that reduces noise by 35 decibels is delivering an enormous improvement in perceived quietness compared to a single-glazed window, even though 35 sounds like a small number in everyday contexts.
What Double Glazing Typically Achieves
Sound reduction performance in windows is expressed using the Rw or STC rating, both of which measure attenuation across a standard range of frequencies. Here is a general guide to what different window types achieve:
- Single glazed aluminium windows: Typically Rw 25 to 28 dB. Provides minimal acoustic insulation against traffic and neighbourhood noise.
- Standard aluminium double glazed windows: Typically Rw 28 to 32 dB, depending on glass thickness and seal quality. A modest improvement over single glazing.
- Double glazed uPVC windows with standard specification: Typically Rw 32 to 38 dB, depending on glass thickness, gap width, and sealing quality.
- Double glazed uPVC windows with acoustic specification: Rw 38 to 42 dB or higher, using asymmetric glass thicknesses, wider gaps, and multi-point sealing.
- Triple glazed uPVC windows: Can achieve Rw values of 42 dB and above, with particularly strong performance at lower frequencies.
What Drives the dB Performance of a Double Glazed Window
The Rw figure for a window depends on several variables that interact with each other. Here is what matters most:
- Glass thickness: Heavier, thicker glass requires more energy to vibrate and attenuates more sound.
- Pane thickness asymmetry: Using different thicknesses on the two panes avoids resonance at matching frequencies, which improves performance across the full frequency range.
- Gap width: Wider gaps provide more acoustic separation. A gap of 12 to 16 millimetres generally performs better acoustically than narrower configurations.
- Frame sealing: Multi-point locking systems that compress perimeter seals fully eliminate the air gaps that allow sound to bypass the glass entirely.
- Frame construction: Rigid uPVC frames with multi-chamber profiles do not transmit vibration and contribute to overall acoustic performance.
What Astellite Offers
Astellite manufactures double and triple glazed windows across homes in Melbourne using German-engineered Aluplast uPVC profiles and high-performance glazing. Products can be specified with acoustic glass options for enhanced noise reduction where required. The range includes tilt and turn windows, fixed windows, awning windows, sliding windows, bifold windows, bay windows, corner windows, and custom windows.
Every window is custom manufactured to your home’s exact dimensions. Astellite holds accreditation from AGWA and WERS, and all products meet Australian building and safety standards. Every installation is backed by a 10-year warranty. The team services homes in Melbourne, Geelong, Melton, and the Mornington Peninsula.
Get a Free Quote Today
Contact us today to arrange your free measure and discuss the right acoustic specification for your home.